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Sync race cache invalidation fixes part 2#14156
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This removes the extra token check and also means we can check membership changes before the token that may get lost due to a stale cache value returned from `get_rooms_for_user`. This can then be used to work around a race between cache invalidation over replication and sync requests.
This avoids race conditions with cache invalidation over replication. Only called for membership changes between two syncs that also don't show up in the get rooms for user call and should thus be sufficiently rare that this doesn't materially impact database performance.
This ensures no race conditions with cache invalidation. Since init syncs are usually new devices or users this is unlikely to impact database performance.
| # If we have no since token (init sync), ensure any cached rooms for the user | ||
| # is first invalidated to avoid race conditions with invalidation-over-replication. | ||
| if not since_token: | ||
| self.store.get_rooms_for_user.invalidate((user_id,)) |
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I'm really hesitant to do this without fully understanding where the inconsistencies are coming in, as per #14154 (comment). In particular, it's not obvious to me that invalidating just this cache won't lead to really weird inconsistencies.
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IIRC this specific change wasn't based on an issue we saw more expected races similar to the other changes here. Probably makes sense to undo this commit, although the invalidating of get_users_in_room probably presents similar inconsistencies. Let's discuss in the issue and come back to this.
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This is now redundant after #14723. |
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See issue: #14154
More involved than the first fix, reviewable commit-by-commit. This essentially serves as a workaround for delayed cache invalidation by utilising the membership events we already pull as part of sync to identify any missing rooms.
Also has two always-invalidate cases for safety. I believe in both of these the frequency of them is so low that the extra invalidation won't be any performance impact.
Signed off by Nick @ Beeper (@Fizzadar).
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